Methods and systems for increasing bandwidth efficiency in satellite communications

ABSTRACT

Methods and systems are provided for increasing bandwidth efficiency in satellite communications. In some embodiments, a satellite communications method is provided that comprises receiving, at a satellite and from a plurality of user ground terminals, a plurality of source signals, wherein each of the source signals are modulated according to at least one source modulation method, and further receiving, at a satellite and from a plurality of user ground terminals, a plurality of information signals corresponding to the plurality of source signals. The method further includes combining, at the satellite, the plurality of source signals into a combined source signal with an overlapping bandwidth, wherein each of the source signals are further modulated according to at least one predetermined modulation method before they are combined, and transmitting, by a downlink transmission from the satellite to a gateway ground station, the combined source signal.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/580,955, filed Nov. 2, 2017, which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present disclosure generally relates to satellite communicationsystems and methods. More particularly, and without limitation, thepresent disclosure relates to systems and methods for increasing thebandwidth efficiency in satellite communication systems.

BACKGROUND

Satellite communication systems relay signals between user groundterminals and gateway ground stations over channels consisting of arange of frequencies. For most coverage areas, the available frequencyspectrum or bandwidth for uplink and downlink satellite transmissions isa limited resource. The growing demand for satellite communications hasthus increased the need for higher levels of bandwidth efficiency, whichcan provide the benefits of increasing capacity in a given bandwidth andreducing pricing to satellite users.

Uplink and downlink transmissions between satellites and terrestrialstations may occur through the use of multiple regional beams and/orspot beams. Examples of beam coverage areas are shown in FIGS. 9 and 10,which illustrate examples of spot beams and regional beams,respectively. Regional beams are wide beams that serve a broader areaand do not require precise directionality to receiving dishes. Forexample, a regional beam might serve the continental United States. Aspot beam, in contrast, is spectrally concentrated in power to cover aspecific, limited geographic area. Spot beams may have radii of, forexample, 300 or 500 miles. Often, neighboring spot beams are clusteredto serve a larger geographic area where the size of the spot beam may bedetermined by factors such as a threshold for loss. For example, theradius of the spot beams may be sized according to locations thatexperience a 3 dB to 7 dB loss relative to the central portion of thebeam that experiences maximum gain.

Neighboring spot beams suffer from mutual interference near their sharedboundaries, and this interference can compound problems relating tolimited bandwidth in satellite transmissions because the interferenceconstrains choice of bandwidth in one spot beam based on its neighboringspot beam. Methods of frequency assignment that involve reusing and/orsharing a portion of the frequency spectrum between satellite spot beamshave been proposed to address the problem of interference andaccompanying inefficiencies in bandwidth usage.

In addition, satellite communications require transmissions overdesignated uplink and downlink channels. Each satellite channel is aspectrum of frequencies. Commonly used frequency bands for satellitecommunications include L-band (1-2 GHz), S-band (2-4 GHz), C-band (4-8GHz), Ku-band (12-18 Ghz), and Ka-band (18-27 GHz). Often, the lowerportion of each band is dedicated to downlink channels, wherein thetransmission is sent from a satellite to the ground, while the upperportion of each band is dedicated to uplink channels, wherein thetransmission is sent from terrestrial stations to the satellite. Totransmit data within a band, source signals are combined with carrierwaves whose frequency is within the band and, more particularly, withina channel.

One method of increasing bandwidth efficiency in satellitecommunications is to modulate individual source signals prior totransmission. For example, Digital Video Broadcasting (DVB) is a familyof standards for modulating source signals in satellite broadcasting.DVB standards include the DVB-S2 and DVB-S2X standards, which providedata framing structures, channel coding, and modulation for combiningindividual source signals with common carrier transmit signals. DVBstandards may involve MPEG compression of data signals for moreefficient bandwidth use.

An additional approach to increasing bandwidth efficiency that may beused in combination with modulation methods like DVB-S2 is to combinesource signals during transmission. DVB standards are designed to carrysingle or multiple compressed MPEG streams (signals) in a singlesatellite transmission, i.e., to transmit multiple source signals onoverlapping channels, which results in more efficient use of theavailable bandwidth.

A number of methods for modulating signals in satellite communicationsnetworks are known in the field. For example, signals may be transmittedusing Frequency Division Multiple Access (FDMA), Time Division MultipleAccess (TDMA), and/or other modulation methods. In FDMA, all users sharea channel comprising a frequency spectrum, but each transmits at aspecific subset of the frequency spectrum within a channel. In TDMA,multiple users share the same channel by transmitting in short burstsalternating with other users. In an example variant of FDMA, OrthogonalFrequency-Division Multiplexing (OFDM), closely neighboring channels andsub-channels are polarized to be orthogonal to one another, decreasingsignal interference. Amplitude Phase Shift Keying (APSK) is anotherexample modulation method, in which the phase and amplitude of a carrierwave are modulated between a finite set of specific amplitudes and phaseshifts to transmit information in a source signal.

Traditional two-carrier channel sharing or carrier-in-carrier channelsharing represents another approach to increasing bandwidth or spectralefficiency, wherein a shared, overlapping bandwidth is used for uplinkand downlink transmissions. Cancellation at both ends of a communicationlink involves providing an estimate or copy of the undesired transmittedsignal to extract the desired received signal from the received combinedsignal.

The above-mentioned techniques suffer from a number of drawbacks,including limitations on bandwidth efficiency and combining multiplesignals into overlapping channels due to interference. For example, TDMAand other such methods do not involve overlapping channels. Also,channels in FDMA are not overlapping but adjacent, as an overlap usingan FDMA-based technique can give rise to signal interference.Furthermore, approaches that involve overlapping signals, likecarrier-in-carrier channel sharing, require access to the originalsource signals to cancel undesired signals and accurately extractdesired signals. This typically limits the overlapping signals to sharethe same uplink and downlink beam.

SUMMARY

Embodiments of the present disclosure provide systems and methods forincreasing bandwidth efficiency in satellite communications. Inaccordance with some embodiments of the present disclosure, systems andmethods are provided that combine two or more source signals intooverlapping frequencies for uplink or downlink transmission in asatellite communications network. The source signals may be combinedeither on the ground or on-board a satellite.

In some embodiments, a combined information signal is also transmittedin the uplink or downlink transmission with the combined source signal.The combined information signal may include information specifying themodulation method to modulate the source signals that are included inthe combined source signal. The combined information signal may alsoinclude other information, such as the source modulation type and errorcorrection code type related to each source signal.

In accordance with an embodiment of the present disclosure, a system forproviding bandwidth efficiency in satellite communications is provided.The system may include one or more receiving antennas at a satellite.The receiving antennas may receive, from a plurality of user groundterminals, a plurality of source signals, wherein each of the sourcesignals are modulated according to at least one source modulationmethod; and a plurality of information signals corresponding to theplurality of source signals. The system may include one or more digitalsignal processors that combine, at the satellite, the plurality ofsource signals into a combined source signal with an overlappingbandwidth. Each of the source signals may further be modulated accordingto at least one predetermined modulation method before they arecombined. The system may include one or more transmitting antennas thattransmit, by a downlink transmission from the satellite to a gatewayground station, the combined source signal. The downlink transmissionmay comprise information specifying a predetermined modulation method.

In accordance with another embodiment of the present disclosure, amethod for providing bandwidth efficiency in satellite communications isprovided. The method may include receiving, at a satellite and from aplurality of user ground terminals, a plurality of source signals. Eachof the source signals may be modulated according to at least one sourcemodulation method. The method may also comprise further receiving, atthe satellite and from the plurality of user ground terminals, aplurality of information signals corresponding to the plurality ofsource signals. In addition, the method may include combining, at thesatellite, the plurality of source signals into a combined source signalwith an overlapping bandwidth. Each of the source signals may be furthermodulated according to at least one predetermined modulation methodbefore they are combined. The method may also comprise transmitting, bya downlink transmission from the satellite to a gateway ground station,the combined source signal, wherein the downlink transmission comprisesinformation specifying the at least one predetermined modulation method.

In accordance with still other disclosed embodiments, non-transitorycomputer readable storage media may store program instructions, whichare executed by at least one processor device and perform any of themethods described herein.

As further disclosed herein, systems and methods consistent with thepresent disclosure may be implemented using a combination ofconventional hardware and software, as well as specialized hardware andsoftware, such as a device or other apparatus constructed and/orprogrammed specifically for performing functions associated with thedisclosed method steps.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof this specification, and together with the description, illustrate andserve to explain the principles of various exemplary embodiments relatedto the present disclosure.

FIG. 1 illustrates an example satellite communications system whereinsignals are separately transmitted on uplink but combined on downlink.

FIG. 2 illustrates an example method for satellite communications,consistent with embodiments of the present disclosure.

FIG. 3 illustrates a more detailed example satellite communicationssystem that can be used to implement the method of FIG. 2.

FIG. 4 illustrates an example satellite communications system whereinsignals are combined on uplink but separately transmitted on downlink.

FIG. 5 illustrates an example method for satellite communications,consistent with embodiments of the present disclosure.

FIG. 6 illustrates a more detailed example satellite communicationssystem that can be used to implement the method of FIG. 5.

FIGS. 7A and 7B illustrate methods consistent with embodiments of thepresent disclosure.

FIG. 8 illustrates the frame structure and contents of an exampleinformation signal.

FIGS. 9 and 10 provide examples of satellite beam coverage areas.

FIG. 11 illustrates a further example satellite communications systemfor embodiments where signals are separately transmitted on uplink butcombined on downlink.

FIG. 12 illustrates a further example satellite communications systemfor embodiments where signals are combined on uplink but separatelytransmitted on downlink.

FIG. 13 illustrates an example satellite communications system forembodiments where signals are separately transmitted on uplink butcombined on downlink.

DETAILED DESCRIPTION

Embodiments of the present disclosure provide systems and methods forincreasing bandwidth efficiency in satellite communications. Embodimentsof the present disclosure combine two or more source signals ofsatellite users into overlapping frequencies for uplink or downlinktransmission in a satellite communications network. To combine sourcesignals, one or more (i.e., “a set of”) digital signal processors (DSPs)may be utilized. For example, to combine source signals for a downlinktransmission, a set of DSPs may be provided on-board a satellite. For anuplink transmission, a set of DSPs may be provided at a gateway groundstation. In both cases, a set of DSPs may also be provided at thecorresponding end of transmission to process and separate out the sourcesignals from the combined source signal.

In some embodiments, a combined information signal is also transmittedin the uplink or downlink transmission with the combined source signal.The combined information signal includes information specifying themodulation method to modulate the source signals that are included inthe combined source signal. The combined information signal alsoincludes other information, such as the source modulation type and errorcorrection code type related to each source signal. In some embodiments,each source signal may have a corresponding information signal. Thecombined information signal may be generated based on the information inthe corresponding information signals, which are originally transmittedor provided with the individual source signals. When the source signalsare combined into an overlapping bandwidth, the combined informationsignals may also be generated and included as part of an uplink ordownlink transmission with the combined source signal (e.g., as part ofa sub-channel or an adjacent or neighboring channel).

Combined source and information signals may be processed at a receivingend of an uplink or downlink transmission to extract the originalsignals. In some embodiments, a set of DSPs at the receiving end of thelink may respectively cancel out component source signal(s) to extractand demodulate the desired source signal(s). By using the information inthe information signal(s), waveform estimation and signal extraction maybe achieved without access to any original source signal. In someembodiments, the estimated waveforms are generated based on informationspecifying the further modulation method for combining the sourcesignals into an overlapping bandwidth.

Embodiments of the present disclosure are advantageous at least becausethey allow two or more source signals to be combined into an overlappingfrequency spectrum without foregoing the capability and signal qualityneeded to ultimately separate and demodulate the signals. For example,in some embodiments, the signals are further modulated or manipulated,before they are combined, to minimize interference and allow the signalsto be subsequently separated without foregoing signal quality. In someembodiments, the signals are subjected to different modulations or thesame modulation method with different parameters. As non-limitingexamples, the signal may be further modulated with different amplitude,phase, delay, or coding before they are combined for transmission.Additionally, as a further example, one or more signal(s) may undergoone or more spectral inversions prior to combining the signals into anoverlapping frequency spectrum. As will be appreciated from the presentdisclosure, embodiments of the invention provide spectral efficiencies(i.e., bps/Hz) that cannot be achieved with traditional satellitecommunication methods.

The disclosed embodiments are additionally advantageous at least becausecancellation of combined source signals may occur without access to theoriginal source signals. Consequently, the disclosed embodiments have awide scope of application because they do not require access to theoriginal source signals. For example, embodiments of the presentdisclosure allow different satellite users, who may be in geographicallydistant locations or beams, to share overlapping frequencies on uplinkand/or downlink channels and achieve higher spectral efficiencies.

As further disclosed herein, information signals consistent with thepresent disclosure may allow the extraction of source signals fromcombined signals without access to the original source signals. Forexample, DSPs of the disclosed embodiments may use a predeterminedmethod of combination and subsequent inverse method of demodulation.Alternatively, or additionally, the use of information signals permitsflexibility in programming the DSPs to adjust the number of source oruser signals that are combined according to the present invention, aswell as the employed modulations methods. Such adjustments can be madeto meet design or system objectives, both of which can change over time.

In some embodiments, the combined information signal may be sent alongwith the combined source signal. The combined information signal can betransmitted at a frequency immediately adjacent to the frequency used totransmit the combined source signal or in a separately allocatedsub-channel or frequency. Upon receipt, cancellation components in theDSPs may make use of information in the combined information signal toextract and demodulate source signals from the combined signals. Theindividual information signals and underlying information related toeach source signals may also be extracted and utilized for subsequentprocessing and routing of the signals.

The disclosed embodiments are distinct from traditional satellitecommunication systems and methods at least because the uplink and/ordownlink channels to a satellite in such systems and methods are notshared or overlapping (either in frequency, beam, or polarization) andat least because signals may be combined either on the ground oron-board a satellite. Many traditional satellite communication systemsand methods transmit over adjacent but non-overlapping frequencies like,for example, FDMA-based methods. The embodiments disclosed herein arealso distinct from two-carrier channel sharing or carrier-in-carrierchannel sharing methods at least because access to the original sourcesignals are not required to cancel and extract the desired sourcesignals from a combined signal.

In some aspects, two or more source signals may originate terrestrially.The source signals may be routed to distinct, remote ground terminals orgateway stations then uplinked to a satellite. In such embodiments, aplurality of received signals at the satellite may be combined by a setof digital signal processors (DSPs) into overlapping channels toincrease bandwidth efficiency for downlink to gateway ground stations.Then, using a set of DSPs on the ground (e.g., at a gateway groundstation), combined signals may be separated into component sourcesignals that are routed terrestrially to the users.

Alternatively, two or more source signals may be routed to a gatewayground station and combined into overlapping frequencies to increasebandwidth efficiency during uplink to the satellite. At the satellite,the combined signal may be cancelled and component signals separated fordownlink to respective user ground terminals and/or gateway stations, asneeded.

FIG. 1 illustrates an example satellite communications system 150wherein source signals are separately transmitted on uplink, butcombined on downlink. For purposes of illustration, example system 150of FIG. 1 is shown with a satellite 107 and two remote user terminals Aand B (101 a, 101 b). It will be appreciated that more than two userterminals could be provided in example satellite system 150. Also, forpurposes of illustration in FIG. 1, there are separate uplinktransmissions of a first source signal (signal A) and a second sourcesignal (signal B) to satellite 107, and a downlink transmission ofcombined source signals (signal (A+B)) to the gateway ground station. Itwill also be appreciated that more than one satellite may be involved inthe transmission of the signals. For example, each source signal andinformation signal may be uplinked from ground terminals to distinctsatellites, then crosslinked to other satellites until ultimatelyarriving at satellite 207, where the signals are combined. As a furtherexample, the combined source signal and corresponding informationsignal(s) may be crosslinked to other satellites prior to downlink tothe ground.

Referring in greater detail to FIG. 1, satellite communication system150 comprises user ground terminal 101 a (User Terminal A) and userground terminal 101 b (User terminal B). Each user ground terminal 101a, 101 b may comprise one or more processors (e.g., DSPs) capable ofgenerating or otherwise providing a source signal and a correspondinginformation signal. Ground terminals 101 a, 101 b may also comprise amodulator for implementing signal modulation and coding schemes. Asfurther shown of FIG. 1, transmitting antennas 100 a, 100 b are alsoprovided at user ground terminals 101 a, 101 b to support and provideuplink transmissions (including source signals 105 a, 105 b andinformation signals 106 a, 106 b) to satellite 107 via uplink spot beams151 a, 151 b or other beams. Transmitting antennas 100 a, 100 b may beco-located with their respective user ground terminals or may bedistributed or remotely located. Also, spot beams 151 a, 151 b may varyin size or shape, or may be implemented as other forms of beams.

In some embodiments, source signals 105 a, 105 b and their respectiveinformation signals 106 a, 106 b may be modulated and exit theirrespective modems or similar communication equipment at ground terminals101 a and 101 b and traverse an uplink transmission path typicallyconsisting of coaxial cables, waveguides, filters, and amplifiersleading to their respective transmitting antennas 100 a, 100 b foruplink transmission. In the example of FIG. 1, a first source signal 105a is uplinked to satellite 107 by antenna 100 a over a first channel anda second source signal 105 b is uplinked to satellite 107 by antenna 100b over a second channel. Information signals 106 a, 106 b to satellite107 are uplinked over distinct channels or sub-channels adjacent to thechannels used by their corresponding source signals 105 a, 105 b. Insome embodiments, the information signals are transmitted on channelsremote from the channels used by their corresponding source signals.

In some embodiments, satellite 107 comprises one or more receive (Rx)antennas and digital pathways to route the source signals and theirrespective information signals to their respective input digital signalprocessor (DSP) ports. Satellite 107 may further comprise one or moretransmit (Tx) antennas for downlink to the ground. Each satellite uplinkpath is not limited to, but may be comprised of, a receive antenna, alow-noise amplifier, a filter, a digital down converter, andmiscellaneous switches, cables, and waveguides. Source signals may ormay not share some common satellite components as they are routed fromtheir respective Rx antennas to their respective DSP ports onboard thesatellite. In some aspects, the DSP(s) will combine source signals, asfurther addressed below. Further, consistent with the presentdisclosure, a combined source signal 111 (A+B) is generated by combiningthe source signals and transmitted out of one of the DSP ports to thesatellite Transmission (Tx) path for transmission to a gateway groundstation 112 via a downlink spot beam 152 or other beam.

Information signals may traverse through some or all of the samecomponents on-board satellite 107 as their corresponding source signal.Further, in some aspects, the corresponding source signal information ineach information signal may be used by DSP(s) at satellite 107 togenerate a combined information signal 110 (Info A+Info B). The combinedinformation signal 110 may follow the downlink Tx path to arrive atgateway ground station 112 via a downlink spot beam 152 or other beam.

Gateway ground station 112 may include a set of DSPs for processing thecombined source signal and combined information signal. By using theinformation in the combined information signal, waveform estimation andsource signal extraction from the combined source signal may be achievedby the DSPs without access to any original source signal. In someembodiments, the estimated waveforms of the source signals are generatedby the DSPs based on information specifying the further modulationmethod(s) (e.g., amplitude shift, phase shift, group delay, spectralinversion, and/or pseudo-noise coding) applied to the source signalsthat have been combined into an overlapping bandwidth. By using theestimated waveforms and signal cancellation (e.g., complex numbercancellation computation) each of the source signals made be extractedby the DSPs from the combined source signal. The extracted sourcesignals can then be routed, with a terrestrial network, to one or moreuser ground terminals.

In some embodiments, the source signals are user signals that comprisecommunication data that gateway ground station 112 ultimately transfersto one or more user terminal(s).

In some embodiments, each signal source is a representation of anyarbitrary source of electronically-transmitted information via acommunication medium. The source signals (A, B) may arrive or originateat user ground terminal 101 a (User terminal A) and user ground terminal101 b (User terminal B). The sources for the signals in the example ofFIG. 1 may be located at the user ground terminal, but it will beappreciated that the signal sources may originate and be modulatedanywhere outside of the user ground terminals 101 a, 101 b and thentransmitted to user ground terminals.

FIG. 2 illustrates an example method for satellite communications,consistent with embodiments of the present disclosure. The examplemethod of FIG. 2 provides a process for combining source signals for adownlink transmission from a satellite to a ground site, such as agateway ground station. At the gateway ground station, estimatedwaveforms are generated and used to extract the individual sourcesignals from the combined source signal. The extracted source signalscan then be routed to one or more user ground terminals.

As shown in FIG. 2, a first source signal (signal A) is uplinked tosatellite 107 from a first user ground terminal 101 a, and a secondsource signal (signal B) is uplinked to satellite 107 from a second userground terminal 101 b. Information signals corresponding to each sourcesignal (dashed lines in FIG. 2) may also be uplinked to the satellite107.

In some embodiments, the source signals and their correspondinginformation signals are modulated at user ground terminals 101 a, 101 bbefore they are uplinked to satellite 107. Alternatively, the sourcesignals and information signals may originate and be modulated anywhereoutside of user ground terminals 101 a, 101 b and then transmitted tothe user ground terminals and subsequently uplinked to satellite 107.Information specifying the original source modulation applied to thesource signal may be provided in the corresponding information signal,along with error correction information and other signal details.

In some embodiments, the source signals (signals A and B) aretransmitted to satellite 107 via orthogonal pathways (e.g., separatefrequencies, beams, or polarizations). The corresponding informationsignals can either be transmitted uplink to satellite 107 at a frequencyimmediately adjacent to the spectrum used to transmit the source signalsor in a separate uplink spectrum distant from the signal source (bothforms of transmission being represented by the dashed line in FIG. 2).In some embodiments, the information signals may be immediately adjacentto the source signals and traverse the same uplink pathways as thesource signals.

At satellite 107, the source signals (signals A and B) are combined onan overlapping bandwidth over a first channel. Information signal A andinformation signal B may also be combined into overlapping frequenciesover a second channel. The combined source signal (source signals A+B)is downlinked by satellite 107 to gateway ground station 112. Inaddition, as part of the downlink, the combined information signal maybe transmitted (represented by the dashed line in FIG. 2).Alternatively, the information signals may be downlinked over separatefrequencies.

In some embodiments, satellite 107 includes a set of DSPs for combiningthe source signals (signals A and B) into a combined source signal withan overlapping bandwidth. In such embodiments, each of the sourcesignals is further modulated according to at least one predeterminedmodulation method (e.g., amplitude shift, phase shift, group delay,spectral inversion, pseudo-noise coding, etc.) before they are combined.The further modulation may be applied to the source signals at the userground terminals or after uplink and on-board the satellite before thesignals are combined to generate the combined source signal. In thedownlink transmission from satellite 107 to gateway ground station 112,the combined source signal is transmitted along with informationspecifying the at least one predetermined modulation method applied aspart of the secondary or further modulation on the source signals.

In some embodiments, a combined information signal is included in thedownlink transmission to gateway ground station 112. The combinedinformation signal may be generated by the DSP(s) on-board satellite 107based on the received information signals and include informationspecifying the at least one predetermined modulation method and furtherinformation related to each of the plurality of source signals that havebeen combined into the combined source signal. In some embodiments, thecombined information signal comprises a modulated parameter specifyingthe at least one predetermined modulation method, and further comprises,for each of the plurality of source signals, one or more of a user ID, asource modulation type, an error correction code type, and a code rate.In some embodiments, for each modulated parameter, a parameter value mayalso be provided in the combined information signal to indicate aparameter value associated with the modulation method.

Referring again to FIG. 2, the combined source signal (A+B) and combinedinformation signal may be processed by gateway ground station 112. Forexample, one or more DSPs at gateway ground station 112 may extract,from the combined information signal, the information specifying the atleast one predetermined modulation method. From the at least onepredetermined modulation method, the DSPs may generate a plurality ofestimated waveforms corresponding to the plurality of source signals.Then, by using signal cancellation (e.g., complex number cancellationcomputation) and the plurality of estimated waveforms, the plurality ofsource signals may be separated from the combined source signal. Inaddition, filtering and demodulation (i.e., the reverse of the furthermodulation method applied to the source signals) may be applied to thesignals. Thereafter, gateway ground station 212 may route, with aterrestrial network or similar communication equipment, the plurality ofsource signals to one or more user ground terminals or other groundsites (i.e., the intended recipients of the source signals).

FIG. 3 illustrates a more detailed example satellite communicationssystem that can be used to implement the method of FIG. 2 and otherembodiments of the present disclosure. The arrangement of components andsteps in FIG. 3 is provided for illustration and is not intended tolimit the invention or the scope of the claims. As will be appreciatedfrom this disclosure, the components and steps of FIG. 3 may be changed,modified, substituted, or rearranged, consistent with the presentdisclosure. For example, while only two source signals and user groundterminals are shown in FIG. 3, it will be appreciated that more than twosource signals and user ground terminals may be included.

In the example embodiment of FIG. 3, each user ground terminal 101 a,101 b includes a set of DSPs (i.e., one or more DSPs) capable of routinga source signal to a set of transmission antennas for uplink 106 a, 106b to satellite 107. Each source signal 103 a, 103 b may include orrepresent electronically-transmitted information via a communicationmedium. The source signals in this example may originate at user groundterminals 101 a, 101 b and be applied with source modulation, or mayoriginate and be modulated outside of the user ground terminals and thentransmitted to the user ground terminals. The DSPs at the user groundterminals 101 a, 101 b may further modulate the source signals 103 a,103 b to provide modulated source signals 104 a, 104 b prior to uplink106 a, 106 b. In this regard, one or more further modulation methods maybe utilized (e.g., amplitude shift, phase shift, group delay, spectralinversion, and/or pseudo-noise coding). Alternatively, source signals103 a, 103 b may be directly uplinked to satellite 107, where thefurther modulation is applied to each source signal before the modulatedsource signals 104 a, 104 b are combined into a combined source signal109.

As further shown in FIG. 3, a first information signal 102 a and asecond information signal 102 b are also provided that correspond toeach source signal 103 a, 103 b. The first and second informationsignals may also be uplinked 105 a, 105 b to satellite 107. In somerespects, the information in the information signals at least allowsDSP(s) on-board satellite 107 to combine the first and second sourcesignals to provide a combined information signal 109. The information inthe information signals may also allow the set of DSP(s) at gatewayground station 112 to apply inverse transforms, signal cancellation,and/or a signal identification method(s) to the received combined sourcesignal to extract the individual source signals 116 a, 116 b, thenoptionally filter 117 a, 117 b those source signals. Although not shownin FIG. 3, gateway ground station 112 may further comprise communicationequipment for routing the source signals to each intended recipient(e.g., via a terrestrial network to one or more user ground terminals).Upon receipt of the routed signals at the user ground terminals or otherground site, demodulation of the source modulation, error correction,and/or other processing steps may be taken, for example.

Referring again to FIG. 3, each information signal 102 a, 102 b may beuplinked 105 a, 105 b to satellite 107, with the uplink beam beingdetermined by user ground terminal 101 a, 101 b based on the position ofsatellite 107 and frequencies assigned to the uplink channel for theinformation signal. Further, each modulated source signal 104 a, 104 bmay be uplinked 106 a, 106 b using, for example, a satellite uplink spotbeam from user ground terminal 101 a, with the uplink beam beingdetermined by user ground terminal 101 a, 101 b based on the position ofsatellite 107 and frequencies assigned to the uplink channel for thesource signal.

In some embodiments, source signals 103 a, 103 b may be routed through aterrestrial network to user ground terminals 101 a, 101 b prior touplink 106 a, 106 b to satellite 107. The terrestrial network (not shownin FIG. 3) may comprise cellular and/or wired communication networks,for example.

In some embodiments, the source modulation method applied to sourcesignals 103 a, 103 b comprises a Digital Video Broadcasting (DVB)standard. For example, the method of source modulation may be DVB-S2 orDVB-S2X.

In some embodiments, the method of modulation for the source signalscomprises at least one Amplitude Phase Shift Key (APSK), FrequencyDivision Multiple Access (FDMA), Time Division Multiple Access (TDMA),Code Division Multiple Access (CDMA), and/or a multiplexing method. Insome embodiments, one or more similar modulation methods may be used forpurposes of applying the further modulation to the source signals.

At satellite 107, the source signals 104 a, 104 b received via uplink106 a, 106 b are combined to generate a combined source signal 109.Combined source signal 109 may comprise first modulated source signal104 a and second modulated source signal 104 b in an overlappingbandwidth. In some embodiments, satellite 107 includes a set of DSPs forcombining source signals 104 a, 104 b into combined source signal 109with an overlapping bandwidth. As previously discussed, each of thesource signals are further modulated according to at least onepredetermined modulation method (e.g., amplitude shift, phase shift,group delay, spectral inversion, pseudo-noise coding, etc.) before theyare combined. The further modulation may be applied to the sourcesignals at user ground terminals 101 a, 101 b (as shown in FIG. 3) orthe further modulation may be applied after uplink and on-boardsatellite 107 before the signals are combined to generate the combinedsource signal 109.

In addition, at satellite 107, a combined information signal 108 may begenerated based on information in the first and second informationsignals 102 a, 102 b received via uplink 105 a, 105 b. In someembodiments, the combined information signal 110 may be generated by theset of DSP(s) on-board satellite 107 based on the received informationsignals 102 a, 102 b and include information specifying the sourcemodulation method as well as the secondary or further modulation methodapplied to the source signals. Combined information signal 111 may alsoinclude other information related to each of the source signals thathave been combined into the combined source signal. An exampleembodiment of a combined information signal is described below withreference to FIG. 8.

In the embodiment of FIG. 3, the satellite uplink path is not limitedto, but typically composed of, one or more receive (Rx) antennas, alow-noise amplifier, a filter, a digital down converter, andmiscellaneous switches, cables, and waveguides. Received source signalsmay or may not share some common satellite components as they are routedfrom their respective Rx antennas to their respective DSP ports on-boardsatellite 107. DSPs may alter and combine the signals to enable greaterbandwidth efficiency on downlinks 110, 111. The DSP may digitize analogsignals using an Analog-to-Digital Converter (ADC). These digitalizedsignals may be filtered and may be routed to either an applicationspecific integrated circuit (ASIC) or field programmable gate array(FPGA) in which the DSP may apply transforms and manipulations tofurther modulate the signals (e.g., by amplitude shift, phase shift,group delay, and/or spectral inversion). Additionally or alternately,the DSP may apply Pseudorandom Noise (PN) coding. As previouslydiscussed, the DSPs of satellite 107 combine the signals such that theyoverlap in frequency. Embodiments may comprise either or bothregenerative and non-regenerative digital signal processorimplementations.

In some embodiments, the combined source signal 109 is generated byoverlapping modulated source signals 104 a, 104 b into overlappingfrequencies to increase bandwidth use. In some embodiments, informationsignals 102 a, 102 b are combined to provide a combined informationsignal 108, wherein the information signals overlap in the same set offrequencies to increase bandwidth use. In some embodiments, informationsignals 102 a, 102 b are not combined into overlapping frequencies butinstead combined information signal 108 is generated at satellite 107 asa new frame or signal including information from signals 102 a, 102 b aswell as other information, such as at least one further modulationmethod. An example embodiment of the frame content and structure of acombined information signal is described below with reference to FIG. 8.

In some embodiments, satellite 107 is implemented as a high throughputsatellite (HTS) and includes one or more digital switch units that areprogrammable and can be used to flexibly assign frequencies and managesatellite communication channels. Each digital switch unit, such asthose commercially available, may enable the provisioning of informationsignals to send parameters to and between satellite 107 and ground sites(including user terminals and gateways). Each digital switch unit mayalso include a set of DSPs (including hardware and functions) forimplementing aspects of the present disclosure, including the combiningand extracting of signals. In some embodiments, the digital switch unitshave built-in algorithms or functions, such as gain, phase, spectralinversion, and/or group delay adjustment capabilities, that are defaulttransform functions. The digital switch units may further comprise oneor more application specific integrated circuits (ASIC) or fieldprogrammable gate arrays (FPGA) that permit signal processing algorithmsor functions to be programmed or otherwise provisioned. In someembodiments, a set of DSPs or equivalent processing components areprovided that are configured to, for example, further modulate theindividual source signals (e.g., by amplitude shift, phase shift, groupdelay, spectral inversion, and/or pseudo-noise coding) and then combinethe source signals such that they overlap in frequency. That is, theprogrammable digital switch units allow the signals to be combined suchthat they are summed together into one overlapping bandwidth, withoutforegoing the capability and signal quality needed to ultimatelyseparate and demodulate the signals. It will be appreciated that theembodiments are not limited to the foregoing examples.

In some embodiments, the DSPs at user ground terminals 101 a, 101 band/or satellite 107 may dynamically change one or more parameters andmethods related to the disclosed embodiments, including the number ofusers/source signals that are combined, the source modulation method,the secondary or further modulation method, and channel-frequencyallocation, for example. The ability to change or dynamically adjustsuch parameters allows an operator to optimize the system utilizationand bandwidth efficiency according to existing needs and the particularsof each coverage area.

Referring again to FIG. 3, combined signals 108, 109 are received viadownlinks 110, 111 by gateway ground station 112. In some embodiments, asignal extraction module 113 of gateway ground station 112 extractscomponent information signals 102 a, 102 b from combined informationsignal 108 using, for example, predetermined demodulation techniques. Inother embodiments, first and second information signals 102 a, 102 b maybe generated at gateway ground station 112 by extracting thecorresponding signal information from combined information signal 108and reconstituting each information signal from that information. Insuch embodiments, a user or channel ID may be provided in combinedinformation signal 108 to designate or mark the correspondinginformation for each information signal/source signal (see FIG. 8below). In cases where signals 102 a, 102 b are combined andsubsequently extracted from combined information signal 108, additionaldemodulation steps on the individual information signals 102 a, 102 bmay be taken by signal extraction module 113.

As further shown in FIG. 3, signal extraction module 113 may useinformation in the information signals 102 a, 102 b to generateestimated waveforms 114 a, 114 b corresponding to the modulated firstand second source signals 104 a, 104 b, respectively, that are includedin combined source signal 109. In some embodiments, signal extractionmodule 113 extracts, from the combined information signal 108, theinformation specifying the secondary or further modulation method, andgenerates, based on the further modulation method, the estimatedwaveforms corresponding to the source signals.

In some embodiments, generating estimated waveforms comprises resamplingthe signal based on the data rate and modulation type specified by theinformation signal. Alternatively, or additionally, in some embodiments,resampling the signal based on the data rate and modulation typespecified by the information signal may allow for the interfering oroverlapping source signal to be estimated, inverted, and reapplied tothe combined waveform for cancellation, yielding the desired waveform.These examples are not limiting, and it will be appreciated that otherembodiments may be utilized for generating estimated waveforms.

With the estimated waveforms 114 a, 114 b, gateway ground station 112can extract the source signals from the combined source signal 109. Asshown in FIG. 3, a signal cancellation module 115 may be provided thatapplies signal cancellation methods to the received combined sourcesignal 109, using the estimated waveforms 114 a, 114 b, to extract andisolate modulated source signals 116 a, 116 b (corresponding to signals104 a, 104 b). For example, signal cancellation module 115 may applycomplex cancellation methods. In the embodiment of FIG. 3, modulatedsource signal 104 a may be isolated 116 a using estimated waveform 114b, and modulated source signal 104 b may be isolated 116 b usingestimated waveform 114 a.

In some embodiments, isolated source signals 116 a, 116 b (correspondingto modulated source signals 104 a, 104 b) may be filtered 117 a, 117 bat gateway ground station 112. Further, as part of the filtering stageor as a subsequent step, demodulation may be performed on the signals(e.g., the reverse of the further modulation method applied to thesignals). In some aspects, the filtering and demodulation may beperformed by the set of DSPs at gateway ground station 112. Thereafter,gateway ground station 112 may route, with a terrestrial network orsimilar communication equipment, the plurality of source signals to oneor more user ground terminals or other ground sites (i.e., the intendedrecipients of the source signals).

FIG. 4 illustrates an example satellite communications system 250wherein source signals are combined and transmitted as a combined sourcesignal on uplink, but separated on downlink. For purposes ofillustration, the example system 250 of FIG. 4 is shown with a satellite212 and two signal sources, Source A (220 a) and Source B (220 b).Signal sources 220 a, 220 b, may be any source for providing a sourcesignal. By way of non-limiting examples, sources 220 a, 220 b maycomprise one or more of a server, a network, a database, a userterminal, a ground site, etc. It will be appreciated that more than twosignal sources 220 a, 220 b could be provided in example satellitesystem 250. Also, for purposes of illustration, in FIG. 4 there isseparate routing of a first source signal 205 a (signal A) and a secondsource signal 205 b (signal B) from signal sources 220 a, 220 b togateway ground station 207; an uplink transmission from gateway groundstation 207 to a satellite 212 of a combined first source signal andsecond source signal (signal (A+B)); and a downlink transmission ofseparated signals source signal A and source signal B to remote userground terminals 201, 201 b. It will also be appreciated that more thanone satellite may be involved in the transmission of signals. Forexample, the combined source signal and corresponding informationsignal(s) may be uplinked from ground gateway station 207 to onesatellite, then crosslinked to other satellites until ultimatelyarriving at satellite 212, where the source signals are separated. As afurther example, the separated source signals may be crosslinked toother satellites prior to downlink to the ground.

Referring in greater detail to FIG. 4, satellite communication system250 comprises two signal sources 220 a, 220 b. Each signal source 220 a,220 b may comprise one or more processors (e.g., DSPs) and/or otherhardware for generating or otherwise providing a source signal and acorresponding information signal. In some embodiments, signal sources220 a, 220 b may comprise a modulator for implementing signal modulationand coding schemes.

In some embodiments, source signals 205 a, 205 b and their respectiveinformation signals may be modulated and exit their respective modems orsimilar communication equipment at signal sources 220 a, 220 b andtraverse a transmission path typically consisting of coaxial cables,waveguides, filters, and amplifiers leading to gateway ground station207. In the example of FIG. 4, first source signal 205 a isterrestrially routed to gateway ground station 207 over a first pathwayand second source signal 205 b is terrestrially routed to gateway groundstation 207 over a second pathway. In addition, a first informationsignal corresponding to the first source signal 205 a is also routed togateway ground station 207 over the same or a different pathway taken byfirst source signal 205 a, and a second information signal correspondingto the second source signal 205 b is also routed to gateway groundstation 207 over the same or a different pathway taken by second sourcesignal 205 b. The information signals may include information regardingthe source modulation method for the corresponding source signals, aswell as error correction information and other details related to thesignal.

In some embodiments, the source signals are user signals that comprisecommunication data that satellite 212 ultimately downlinks via spotbeam(s) 251 a, 251 b or other beam(s) to one or more user terminal(s)201 a, 201 b. As will be appreciated, spot beams 251 a, 251 b may varyin size or shape, or may be implemented as other form of beams.

In some embodiments, each signal source is a representation of anyarbitrary source of electronically-transmitted information via acommunication medium. The source signals 205 a, 205 b may arrive ororiginate at signal source 220 a and signal source 220 b, as shown inFIG. 4.

Gateway ground station 207 includes one or more DSPs and one morereceiving modems or similar equipment that routes received sourcesignals and received information signals for processing. In someaspects, the DSP(s) will combine the received source signals into acombined source signal. For example, consistent with the presentdisclosure, a combined source signal 211 (A+B) is generated by combiningthe source signals into overlapping frequencies at gateway groundstation 207 and may be transmitted out of one of the DSP ports to agateway ground Transmission (Tx) path for uplink transmission tosatellite 212. The uplink may occur over a spot beam 252 or other beams.

In some embodiments, gateway ground station 207 includes one or moreprogrammable digital switch units that can flexibly assign frequenciesand manage satellite communication channels. Each digital switch unitmay enable the provisioning of information signals to send parameters toand between satellite 207 and ground sites (including user terminals andgateways). DSPs at the gateway ground station 207 may be capable ofimplementing aspects of the present disclosure, including the combiningand extracting of signals. Each digital switch unit may have built-inalgorithms, such as gain, phase, spectral inversion, and/or group delayadjustment capabilities, that are default transform functions. Thedigital switch units may further comprise one or more applicationspecific integrated circuits (ASIC) or field programmable gate arrays(FPGA) that permit signal processing algorithms or functions to beprogrammed or otherwise provisioned. In some embodiments, a set of DSPsor equivalent processing components are provided that are configured to,for example, further modulate the individual source signals (e.g., byamplitude shift, phase shift, group delay, spectral inversion, and/orpseudo-noise coding) and then combine the source signals such that theyoverlap in frequency. That is, the programmable digital switch unitsallow the signals to be combined such that they are summed together intoan overlapping bandwidth, without foregoing the capability and signalquality needed to ultimately separate and demodulate the signals. Itwill be appreciated that the embodiments are not limited to theforegoing examples.

Further, the set of DSPs in gateway ground station 207 may generate acombined information signal from the received information signals. Insome embodiments, the information in each information signal is used byDSP(s) at gateway ground station 207 to generate a combined informationsignal (Info A+Info B). An example of a combined information signal isprovided in FIG. 8. The combined information signal may follow thegateway ground Transmission (Tx) path for uplink transmission tosatellite 212.

In some embodiments, satellite 212 comprises one or more receive (Rx)antennas and digital pathways to route the combined source signal (A+B)and combined information signal to input digital signal processor (DSP)ports. Each satellite uplink path is not limited to, but may becomprised of, one or more receive antennas, a low-noise amplifier, afilter, a digital down converter, and miscellaneous switches, cables,and waveguides. Satellite 212 further comprises one or more Tx antennasfor downlink to the ground.

In the embodiment of FIG. 4, signal cancellation module(s) in DSPs onsatellite 212 may separate the combined source signal into componentsource signal A and source signal B. Also, signal extraction module(s)in DSPs on satellite 212 may separate combined information signals intocomponent information signal A and information signal B.

Satellite 212 may include a set of DSPs for processing the combinedsource signal and combined information signal. By using the informationin the combined information signal, waveform estimation and sourcesignal extraction from the combined source signal may be achieved by theDSPs without access to any original source signal. In some embodiments,the estimated waveforms of the source signals are generated by the DSPsbased on information specifying the further modulation method(s) (e.g.,amplitude shift, phase shift, group delay, spectral inversion, and/orpseudo-noise coding) applied to the source signals that have beencombined into an overlapping bandwidth. By using the estimated waveformsand signal cancellation (e.g., complex number cancellation computation)each of the source signals made be extracted by the DSPs from thecombined source signal. The extracted source signals can then be routed,with a terrestrial network, to one or more user ground terminals.

FIG. 5 illustrates an example method for satellite communicationsconsistent with the present disclosure. The example method of FIG. 5provides a process for combining source signals for an uplink, andsubsequently extracting the individual source signals at the receivedend of the transmission on-board a satellite. At the satellite,estimated waveforms are generated and used to extract the individualsource signals from the combined source signal. The extracted sourcesignals can then be downlinked via spot beams or other beams to one ormore user ground terminals or other ground sites.

As shown in FIG. 5, a first source signal (signal A) is routed from afirst signal source 220 a to a gateway ground station 207, and a secondsource signal (signal B) is routed to gateway ground station 207 from asecond signal source 220 b. Information signals corresponding to eachsource signal (dashed lines in FIG. 5) may also be routed to gatewayground station 207.

In some embodiments, the source signals and their correspondinginformation signals are modulated at signal sources 220 a, 200 b beforethey are routed to gateway ground station 207. Information specifyingthe original source modulation applied to the source signal may beprovided in the corresponding information signal, along with errorcorrection information and other signal details.

At gateway ground station 207, the source signals (signals A and B) arecombined on an overlapping bandwidth over a first channel. Informationsignal A and information signal B may also be combined into overlappingfrequencies over a second channel. Alternatively, a combined informationsignal (see, e.g., FIG. 8) may be generated from the receivedinformation signals. The combined source signal (A+B) is then uplinkedto satellite 212. In some embodiments, as part of the same channel or arelated sub-channel for the uplink of the combined source signal, thecombined information signal is transmitted (represented by the dashedline in FIG. 5) to satellite 212. Alternatively, the combinedinformation signal may be uplinked over separate frequencies.

In some embodiments, gateway ground station 207 includes a set of DSPsfor combining the source signals (signals A and B) into a combinedsource signal with an overlapping bandwidth. In such embodiments, eachof the source signals is further modulated according to at least onepredetermined modulation method (e.g., amplitude shift, phase shift,group delay, spectral inversion, pseudo-noise coding, etc.) before theyare combined. The further modulation may be applied to the sourcesignals at signal sources 220 a, 220 b or gateway ground station 207before the signals are combined to generate the combined source signal.In the uplink transmission from gateway ground station 207 to satellite212, the combined source signal is transmitted along with informationspecifying the at least one predetermined modulation method applied aspart of the secondary or further modulation on the source signals.

In some embodiments, a combined information signal is included in theuplink transmission to satellite 212. The combined information signalmay be generated by the DSP(s) of the gateway ground station 207 basedon the received information signals and include information specifyingthe at least one predetermined modulation method and further informationrelated to each of the plurality of source signals that have beencombined into the combined source signal. In some embodiments, thecombined information signal comprises a modulated parameter specifyingthe at least one predetermined modulation method, and further comprises,for each of the plurality of source signals, one or more of a user ID, asource modulation type, an error correction code type, and a code rate.In some embodiments, for each modulated parameter, a parameter value mayalso be provided in the combined information signal to indicate aparameter value associated with the modulation method.

Referring again to FIG. 5, the combined source signal (A+B) and combinedinformation signal may be processed by satellite 212. For example, oneor more DSPs at the satellite 212 may extract, from the combinedinformation signal, the information specifying the at least onepredetermined modulation method. From the at least one predeterminedmodulation method, the DSPs may generate a plurality of estimatedwaveforms corresponding to the plurality of source signals. Then, byusing signal cancellation (e.g., complex number cancellationcomputation) and the plurality of estimated waveforms, the plurality ofsource signals may be separated from the combined source signal. Inaddition, filtering and demodulation (e.g., the reverse of the furthermodulation method applied to the source signals) may be applied to thesignals. Thereafter, satellite 212 may downlink the plurality of sourcesignals to one or more user ground terminals or other ground sites(i.e., the intended recipients of the source signals) via spot beams orother beams.

FIG. 6 illustrates a more detailed example satellite communicationssystem that can be used to implement the method of FIG. 5 and otherembodiments of the present disclosure. The arrangement of components andsteps in FIG. 6 is provided for illustration and is not intended tolimit the invention or the scope of the claims. As will be appreciatedfrom this disclosure, the components and steps of FIG. 6 may be changed,modified, substituted, or rearranged, consistent with the presentdisclosure. For example, while only two source signals and user groundsignal source stations are shown in FIG. 6, it will be appreciated thatmore than two source signals and user ground signal source stations maybe included

In the example embodiment of FIG. 6, each signal source 220 a, 220 bincludes a set of DSPs (i.e., one or more DSPs) and a set of modemsand/or similar equipment capable of terrestrially routing source signalsto a gateway ground station 207. Each source signal 203 a, 203 b mayrepresent electronically-transmitted information via a communicationmedium. The DSPs at the signal sources 220 a. 220 b may be capable ofmodulating the source signals 204 a, 204 b prior to routing 206 a, 206b. In this regard, one or more further modulation methods may beutilized (e.g., amplitude shift, phase shift, group delay, spectralinversion, and/or pseudo-noise coding). Alternatively, source signals203 a, 203 b may be directly routed to gateway ground station 207, wherethe further modulation is applied to each source signal before themodulated source signals 204 a, 204 b are combined into a combinedsource signal 209.

As further shown in FIG. 6, a first information signal 202 a and asecond information signal 202 b are also provided that correspond toeach source signal 203 a, 203 b. The first and second informationsignals may also be terrestrially routed 205 a, 205 b to gateway groundstation 207. In some embodiments, the information in the informationsignals at least allows DSP(s) at gateway ground station 207 to combinethe first and second source signals 209. The information in theinformation signals additionally allows DSP(s) capable of carrierextraction 215 in satellite 212 to apply inverse transforms, signalcancellation, and/or a signal identification method to the receivedcombined source signal to extract the individual source signals 216 a,216 b, then optionally filter 217 a, 217 b the source signals. Althoughnot shown in FIG. 6, satellite 212 further comprises downlink Txantennas capable of transmitting the source signals to each intendedrecipient. Upon receipt at the user ground terminals or other groundsite, demodulation of the source modulation, error correction, and otherprocessing steps may be performed, for example.

Referring again to FIG. 6, information signals 202 a, 202 b, andmodulated source signal 204 a, 204 b may be routed over a terrestrialnetwork to gateway ground station 207. The terrestrial network maycomprise cellular and/or wired communication networks.

In some embodiments, the source modulation method applied to sourcesignals 203 a, 203 b comprises a Digital Video Broadcasting (DVB)standard. For example, the method of source modulation may be DVB-S2 orDVB-S2X.

In some embodiments, the method of modulation for the source signalscomprises at least one Amplitude Phase Shift Key (APSK), FrequencyDivision Multiple Access (FDMA), Time Division Multiple Access (TDMA),Code Division Multiple Access (CDMA), and/or a multiplexing method. Insome embodiments, one or more similar modulation methods may be used forpurposes of applying the further modulation to the source signals.

At gateway ground station, 207, the received source signals 204 a, 204 bare combined to generate a combined source signal 209. Combined sourcesignal 209 may comprise first modulated source signal 204 a and secondmodulated source signal 204 b in an overlapping bandwidth. In someembodiments, gateway ground station 207 includes a set of DSPs forcombining source signals 204 a, 204 b into combined source signal 209with an overlapping bandwidth. As previously discussed, each of thesource signals are further modulated according to at least onepredetermined modulation method (e.g., amplitude shift, phase shift,group delay, spectral inversion, pseudo-noise coding, etc.) before theyare combined. The further modulation may be applied to the sourcesignals at signal source 220 a, 220 b (as shown in FIG. 6) or thefurther modulation may be applied at gateway ground station 207 beforethe signals are combined to generate the combined source signal 209.

In addition, at gateway ground station 207, a combined informationsignal 208 may be generated based on information in the first and secondinformation signals 202 a, 202 b. In some embodiments, combinedinformation signal 208 may be generated by the set of DSP(s) at gatewayground station 207 based on the received information signals 202 a, 202b and include information specifying the source modulation method aswell as the secondary or further modulation method applied to the sourcesignals. Combined information signal 208 may also include otherinformation related to each of the source signals that have beencombined into the combined source signal. An example embodiment of acombined information signal is described below with reference to FIG. 8.

In the embodiment of FIG. 6, the signals are routed to the set of DSPsat gateway ground station 207. The received source signals may or maynot share some common components as they are routed from theirrespective DSP ports at gateway ground station 207. The set of DSPs mayalter and combine the source signals to enable greater bandwidthefficiency on the uplink 211 to satellite 212. The DSPs may digitizeanalog signals using an Analog-to-Digital Converter (ADC). Thesedigitalized signals may be filtered and may be routed to either anapplication specific integrated circuit (ASIC) or field programmablegate array (FPGA) in which the DSPs may apply transforms andmanipulations that may modify the amplitude, phase, group delay, and/orspectral inversion. Additionally or alternately, the DSPs may applyPseudorandom Noise (PN) coding. As previously discussed, the DSPs ofgateway ground station 207 combine the signals such that they overlap infrequency. Embodiments may comprise either or both regenerative andnon-regenerative digital signal processor implementations.

In some embodiments of FIG. 6, the combined source signal 209 isgenerated by overlapping further modulated source signals 204 a, 204 binto overlapping frequencies to increase bandwidth use. For example, insome embodiments, the signals are further modulated or manipulated,before they are combined, to minimize interference and allow the signalsto be subsequently separated without foregoing signal quality. In someembodiments, the signals are subjected to different modulations or thesame modulation method with different parameters. As non-limitingexamples, the signal may be further modulated with different amplitude,phase, delay, or coding before they are combined for transmission.Additionally, as a further example, one or more signal(s) may undergoone or more spectral inversions prior to combining the signals into anoverlapping frequency spectrum. As will be appreciated from the presentdisclosure, embodiments of the invention provide spectral efficiencies(i.e., bps/Hz) that cannot be achieved with traditional satellitecommunication methods.

In some embodiments, information signals 202 a, 202 b are combined toprovide a combined information signal 208, wherein the informationsignals overlap in the same set of frequencies to increase bandwidthuse. In some embodiments, information signals 202 a, 202 b are notcombined into overlapping frequencies but instead combined informationsignal 208 is generated at gateway ground station 207 as a new frame orsignal including information from signals 202 a, 202 b as well as otherinformation, such as the further modulation method. An exampleembodiment of the frame content and structure of a combined informationsignal is described below with reference to FIG. 8.

In some embodiments, digital signal processors at one or more signalsources 220 a, 220 b, gateway ground station 207, and/or satellite 212may dynamically change one or more parameters and methods related to thedisclosed embodiments, including the number of users/source signals thatare combined, the source modulation method, the secondary or furthermodulation method, and channel-frequency allocation, for example. Theability to change or dynamically adjust such parameters allows anoperator to optimize the system utilization and bandwidth efficiencyaccording to existing needs and the particulars of each coverage area.

Referring again to FIG. 6, combined signals 208, 209 are received viauplinks 210, 211 to satellite 212.

In some embodiments, satellite 212 is implemented as a high throughputsatellite (HTS) and includes one or more digital switch units that areprogrammable and can be used to flexibly assign frequencies and managesatellite communication channels. Each digital switch unit, such asthose commercially available, may enable the provisioning of informationsignals to send parameters to and between satellite 212 and ground sites(including user terminals and gateways). Each digital switching unit mayinclude a set of DSPs (including hardware and functions) forimplementing the above aspects of the present invention, including thecombining and extracting of signals. In some embodiments, the digitalswitch units have built-in algorithms or functions, such as gain, phase,spectral inversion, and/or group delay adjustment capabilities, that aredefault transform functions. The digital switch units may furthercomprise one or more application specific integrated circuits (ASIC) orfield programmable gate arrays (FPGA) that permit signal processingalgorithms or functions to be programmed or otherwise provisioned. Insome embodiments, a set of DSPs or equivalent processing components areprovided that are configured to, for example, further modulate theindividual source signals (e.g., by amplitude shift, phase shift, groupdelay, spectral inversion, and/or pseudo-noise coding) and then combinethe source signals such that they overlap in frequency. That is, theprogrammable digital switch units allow the signals to be combined suchthat they are summed together into an overlapping bandwidth, withoutforegoing the capability and signal quality needed to ultimatelyseparate and demodulate the signals. It will be appreciated that theembodiments are not limited to the foregoing examples.

In some embodiments, a signal extraction module 213 of satellite 212extracts component information signals 202 a, 202 b from the combinedinformation signal 208 using, for example, predetermined demodulationtechniques. In other embodiments, first and second information signals202 a, 202 b may be generated at satellite 212 by extracting thecorresponding signal information from combined information signal 208and reconstituting each information signal from that information. Insuch embodiments, a user or channel ID may be provided in combinedinformation signal 208 to designate or mark the correspondinginformation for each information signal/source signal (see FIG. 8below). In cases where signals 202 a, 202 b are combined andsubsequently extracted from combined information signal 208, additionaldemodulation steps on the individual information signals 202 a, 202 bmay be taken by signal extraction module 213.

As further shown in FIG. 6, signal extraction module 213 may useinformation in information signals 202 a, 202 b to generate estimatedwaveforms 214 a, 214 b corresponding to the modulated first and secondsource signals 204 a, 204 b, respectively, that are included in combinedsource signal 209. In some embodiments, signal extraction module 213extracts, from the combined information signal 208, the informationspecifying the secondary or further modulation method, and generates,based on the further modulation method, the estimated waveformscorresponding to the source signals.

In some embodiments, generating estimated waveforms comprises resamplingthe signal based on the data rate and modulation type specified by theinformation signal. Alternatively, or additionally, in some embodimentsresampling the signal based on the data rate and modulation typespecified by the information signal may allow for the interfering oroverlapping source signal to be estimated, inverted, and reapplied tothe combined waveform for cancellation, yielding the desired waveform.These examples are not limiting, and it will be appreciated that otherembodiments may be utilized for generating estimated waveforms.

With the estimated waveforms 214 a, 214 b, satellite 212 can extract thesource signals from the combined source signal 209. As shown in FIG. 6,a signal cancellation module 215 may be provided that applies signalcancellation methods to the received combined source signal 209 and theestimated waveforms 214 a, 214 b to extract and isolate modulated sourcesignals 216 a, 216 b. For example, the signal cancellation module 215may apply complex cancellation methods. In the embodiment of FIG. 6,modulated source signal 204 a may be isolated 216 a using estimatedwaveforms 214 b, and modulated source signal, 204 b may be isolated 216b using estimated waveforms 214 a.

In some embodiments, each isolated source signals 216 a, 216 b(corresponding to modulated source signals 204 a, 204 b) may be filtered217 a, 217 b at satellite 212. Further, as part of the filtering stageor as a subsequent step, demodulation may be performed on the signals(i.e., the reverse of the further modulation method applied to thesignals). In some aspects, the filtering and demodulation may beperformed by the set of DSPs at satellite 212. Thereafter, satellite 212may downlink, with one or more downlink Tx antennas, the plurality ofsource signals to one or more user ground terminals or other groundsites (i.e., the intended recipients of the source signals).

FIG. 7A illustrates a flowchart of an example method of combining sourcesignals into an overlapping bandwidth, consistent with the presentdisclosure. The example method of FIG. 7A may be applied to generate acombined source signal at a satellite (for a downlink transmission or agateway ground station (for an uplink transmission).

At step 700, a plurality of source signals and a plurality ofcorresponding information signals are received. In some embodiments, thesource signals and information signals are received, via uplink, by oneor more receiving antennas on-board a satellite. For example, theplurality of source signals and corresponding information signals may betransmitted from two or more user ground terminals via transmissionantennas to the receiving antennas of a satellite. As a further example,the source and information signals may be transmitted from one or moregateway ground stations to a satellite.

In other embodiments, the plurality of source signals and informationsignals are received at a gateway ground station. For example, thesource signals and information signals may be received at a gatewayground station by one or more ports. In such cases, the source andinformation signals may be routed from two more user ground terminalsvia, for example, a transmission path (e.g., comprising of coaxialcables, waveguides, filters, and amplifiers) leading to the gatewayground station. The transmission path may comprise cellular and/or wiredcommunication networks.

In some embodiments, the received information signals includeinformation relating to a source modulation method of the correspondingsource signal. The plurality of received information signals may alsoinclude information specifying a secondary or further method ofmodulation applied to the corresponding source signal before it wascombined with other source signal(s) in an overlapping bandwidth.

Referring again to FIG. 7A, at step 702, the received source signals maybe combined to form a combined source signal. A secondary or furthermodulation method may be applied to the source signals before they arecombined. As part of step 702, the source signals may be combined intoan overlapping bandwidth. The signals may also be further combined usinga set of digital signal processors (DSPs). In some embodiments, the DSPsare located on-board a satellite. In other embodiments, the DSPs arelocated at a gateway ground station.

At step 704, the combined source signal and information specifying thesecondary or further modulation method are transmitted (e.g., from asatellite (downlink) or a gateway ground station (uplink)). In someembodiments, the transmission may be from antenna(s) on a satellite fordownlink to receiving antenna(s) at a gateway ground station. In otherembodiments, the transmission may be from antenna(s) at a gateway groundstation for uplink to receiving antenna(s) on-board a satellite. Ineither case, the combined source signal and information is transmittedon an overlapping bandwidth, thus increasing spectral efficiency. Also,as disclosed herein, the information specifying the secondary or furthermodulation method may be transmitted as part of a combined informationsignal.

FIG. 7B illustrates a flowchart of an example method for receiving andseparating a combined source signal into individual source signals withnon-overlapping bandwidth for transmission, consistent with the presentdisclosure. The method of FIG. 7B can be used in combination with (andsubsequent to) the method of FIG. 7A, described above. The examplemethod of FIG. 7B and related processing of the combined source signalmay be performed at a gateway ground station (that has received thecombined signal as part of a downlink transmission) or at a satellite(that has received the combined signal as part of an uplinktransmission).

At step 710, the combined source signal is received, along withinformation specifying a secondary or further modulation method appliedto the source signals before they were combined. In some embodiments,the combined source signal is received via an uplink to receivingantenna(s) of a satellite. In other embodiments, the combined sourcesignal is received via a downlink from a satellite to receivingantenna(s) of a gateway ground station. In addition to receiving thecombined source signal, a combined information signal may be received.As disclosed herein, the combined information signal may includeinformation specifying the secondary or further modulation methodapplied to the source signals before they were combined.

In some embodiments, the information specifying the further modulationmethod is extracted from the combined information signal, which alsoincludes other information related to the individual source signals inthe combined source signal. In some embodiments, a combined informationsignal is not utilized and instead the information specifying thefurther modulation method may be extracted from one or more receivedinformation signals corresponding to the individual source signals inthe combined source signal.

In some embodiments, information specifying the further modulationmethod is extracted by separating a received combined information signalusing a predetermined demodulation method and analyzing the informationin the plurality of information signal using a set of DSPs. In someembodiments, extracting information specifying the further modulationmethod comprises analyzing information in a combined information signal,or in a plurality of information signals, whichever is received, using aset of DSPs.

Step 712 comprises generating estimated waveforms based on theinformation specifying the further modulation method (extracted in step710). In some embodiments, signal extraction module extracts, from thecombined information signal 108, the information specifying thesecondary or further modulation method, and generates, based on thefurther modulation method, the estimated waveforms corresponding to themodulated source signals that are combined into the combined sourcesignal.

As further shown in FIG. 7B, step 714 comprises generating, by signalcancellation, the individual source signals from the combined sourcesignal. For example, the signals may be generated by applying theestimated waveforms to the combined source signal and using complexcancellation methods. In some embodiments, each isolated source signal(corresponding to modulated source signals in the combined sourcesignal) may be filtered, either at a satellite or a gateway groundstation, depending on where the processing is performed. Further, aspart of a filtering stage or as a subsequent step, demodulation may beperformed on the signals (i.e., the reverse of the further modulationmethod applied to the signals). In some aspects, the filtering anddemodulation may be performed by a set of DSPs at the satellite orgateway ground station. Thereafter, the signals may be routed, with aterrestrial network or similar communication equipment, to one or moreuser ground terminals or other ground sites (i.e., the intendedrecipients of the source signals).

FIG. 8 illustrates the frame structure and contents of an examplecombined information signal 801. The combined information signal 801 maybe employed with embodiments of the present disclosure, including thatdescribed above. As disclosed herein, a combined information signal mayprovide information regarding the source modulation method and otherdetails (error correction code type, code ratio, etc) related to eachsource signal, as well as the further modulation method(s) applied tothe sources signals before they are combined into a combined sourcesignal. The combined information signal may be generated based on thesource information signals and transmitted with the combined sourcesignal (e.g., in a related sub-channel).

The combined information signal contains all of the information neededto generate the estimated waveforms to isolate the source signals ofinterest (i.e., each source or user signal) from the combined sourcesignal. The combined information signal can be routed (controlled viaground command) to the section of the DSP(s) that process users that arecombined in overlapping frequency for separation.

In some embodiments, the combined information signal containsinformation that informs an extraction module or similar module of theDSP(s) about the composition (source modulation type, code rate, etc.)of each source signal and the further modulations (e.g., frequencyoffset, phase offset, shaping factor, phase, amplitude, and/or groupdelay shifts) added to the signal to produce the combined source signal.Based on the contents of the combined information signal, the DSP(s) areable to generate estimated waveforms corresponding to each of the sourcesignals which is used in a signal cancellation module or similar moduleof the DSP(s) to respectively cancel out other source signal(s), leavingeach source signal of interest remaining intact.

As noted above, FIG. 8 illustrates the frame structure and contents ofthe combined information signal 801. It will be appreciated from thisdisclosure that other forms and arrangements are possible and that theexample shown in FIG. 8 is merely for purposes of illustration. Ingeneral, combined information signal 801 may be composed of a sequenceof bits in a frame structure. As noted above, combined informationsignal 801 can be used to aid in the separation of source signals(corresponding to User 1 to User N in FIG. 8) that overlap in frequency.

As shown in the example embodiment of FIG. 8, a Preamble is provided aspart of combined information signal 801. The Preamble may consist of apredetermined number of bits (e.g., 16 bits) that provides goodcorrelation properties to enhance detection of the information signalduring signal processing. In some embodiments, the Preamble includes aunique bit sequence to mark the start of the frame.

The frame structure of combined information signal 801 also includesinformation related to each of the source signals that are combined fortransmission (uplink or downlink). In FIG. 8, information related to thesource signals of User 1 to User N is shown, where N can any numbergreater than 1 (i.e., a minimum of two is required). It will beappreciated that the complexity of the processing increases with thenumber of source or user signals. In some embodiments, the number ofcombined source signals is 2. In other embodiments, N equals 3, 4, or 5.The level of processing complexity that can be supported will depend onthe set of DSP(s) provided on-board the satellite or at the groundstations.

For each User 1 to User N, the example combined information signal 801includes a User ID field and a Modulation Type, a Modulated Parameter, aParameter Value, a Code Type, and a Code Rate that follow this field.The User ID comprises a unique sequence to identify the user. In theexample embodiment of FIG. 8, the User ID filed is 10 bits. By way ofexample, the sizes of the other fields are: Modulation Type (6 bits),Modulated Parameter (4 bits), Parameter Value (64 bits), Code Type (6bits), and Code Rate (8 bits), as further shown in FIG. 8.

The Modulation Type may indicate the type of source modulation used forthe corresponding source signal (e.g., QPSK, 16-QAM, 64 APSK, etc.). TheModulated Parameter may provide information regarding the secondary orfurther modulation method(s) (e.g., amplitude shift, phase shift, groupdelay, spectral inversion, and/or pseudo-noise coding). The ParameterValue may provide further information related to the further modulationmethod, such as the quantified adjustment of the Modulated Parameter(e.g., a 90 degree phase shift, in the case of phase shift to the sourcesignal). The Modulated Parameter and Parameter Value may be used by theDSP(s) to aid in the separation of the overlapping signals.

As disclosed herein, the secondary or further modulation may bepredetermined or programmed in advance. Also, each source signal may befurther modulated in advance by the DSP(s) before they are combined. Insome embodiments, the predetermined modulation method is the same forall source signals to be combined. In other embodiments, the modulationmethod (as reflected by the Modulated Parameter and Parameter Value)varies with respect to the source signals to be combined. In eithercase, as reflected in the example of FIG. 8, the combined informationsignal includes not only the underlying source modulation for eachsource signal, but also the secondary or further modulation applied toeach source signal.

Referring again to FIG. 8, the information for each source or usersignal also includes a Code Type and Code Rate. The Code Type mayprovide information related to the type of error correction employed forthe source signal, such as a Forward Error Correction (FEC) code (e.g.,LDPC, Reed-Solomon, Convolutional, etc.). The Code Rate may provideinformation that indicates the ratio of information bits to errorcorrection bits (e.g., 7/8).

Other information may be provided as part of combined information signal801, such as a Checksum. This field (16 bits in the example of FIG. 8)may provide an integer quantity that is the output of an errorcorrection algorithm. For example, the Checksum field may provide theoutput integer value of a CRC (Cyclic Redundancy Check) algorithm usedto determine if a bit error has occurred in the received frame.

FIGS. 11 and 12 illustrate further examples of satellite communicationssystems for implementing embodiments of the invention, including theabove embodiments for FIGS. 7A and 7B. FIG. 11 illustrates an examplesatellite communications system for embodiments where signals areseparately transmitted on uplink but combined on downlink. In FIG. 11,the system elements are shown along with the steps or operations thatare performed by the system elements. As shown in FIG. 11, a pluralityof ground equipment stations 1102, 1104 may be provided, wherein eachground equipment station includes a ground info signal generator, aground modem, and a user uplink antenna. A plurality of info signals andusers signals/waveforms are transmitted via the uplink antenna tosatellite equipment 1106 on board a satellite. A DSP on board thesatellite may combine the plurality of info signals into one subchannelbandwidth. Further, the DSP may combine the plurality of usersignals/waveforms into an overlapping bandwidth within the channel. Adownlink gateway antenna may transmit the combined info signal and thecombined user signals to ground equipment 1108. A ground DSP extractionmodule 1110 in the ground equipment may separate info signals andextracts parameters (e.g., modulation parameters). The DSP extractionmodule 110 may also generate estimated waveforms based on theparameters. In some embodiments, using complex cancellation computationmethods, a ground signal cancellation module 1112 separates the combineduser signal into two or more user signals. Separated user signals may berouted to users on the ground, consistent with the disclosedembodiments.

FIG. 12 illustrates a further example satellite communications systemfor embodiments where signals are combined on uplink but separatelytransmitted on downlink. In FIG. 12, the system elements are shown alongwith the steps or operations that are performed by the system elements.As shown in FIG. 12, ground equipment 1202 is provided that may includea ground info signal generator, a ground model signal combiner, and agateway uplink antenna. The ground signal generator may generate acombined info signal, consistent with the disclosed embodiments.Further, the ground modem signal combiner may generate a combined usersignal, consistent with the disclosed embodiments. The combined infosignal and combined user signal may be transmitted to satelliteequipment 1204 on board a satellite via a gateway uplink antenna. A DSPextraction module 1206 on board the satellite may separate info signalsand extract parameters (e.g., modulation parameters). Further, the DSPextraction module 1206 may generate estimated waveforms based on theparameters. In some embodiments, using complex cancellation computationmethods, a signal cancellation module 1208 separates the combined usersignal into two or more user signals. Separated user signals may bedownlinked via a spot beam, for example and demodulated on the ground.

The following table indicates the increased spectral efficiency andthroughput that can be achieved by combining two source signals in anoverlapping bandwidth, consistent with the present disclosure. The tableis provided for illustration and is not exhaustive of the advantageousof the present disclosure.

TABLE 1 Examples of Data Rates, Modulations, and Code Rates SpectralThroughput Throughout Efficiency for 1 MHz for Improvemnet BandwidthSpectral 1 MHz with with Efficiency with Bandwidth OverlappingOverlapping Traditional Traditional Source Source Modulation & CodingModems Modems Signals Signals Receive Antenna (bps/Hz) (Mbps) (bps/Hz)(Mbps) QPSK 39/50 FEC-0.83 m 1.30 1.30 2.60 2.60 16QAM 7/8 FEC-2.4 m2.67 2.67 5.33 5.33 16APSK 0.6244 FEC-1.2 m 2.08 2.08 4.16 4.16 32APSK29/40 FEC-2.4 m 3.02 3.02 6.04 6.04 64-APSK 144/180 FEC-2.4 m 3.79 3.797.58 7.58 256-APSK 29/45 FEC-1.8 m 4.73 4.73 9.46 9.46 256-APSK 3/4FEC-3.8 m 5.44 5.44 10.87 10.87

FIG. 13 illustrates, in accordance with the present disclosure, anexample satellite communications system 1300 for embodiments wheresource signals are separately transmitted on uplink, but combined ondownlink. Traditional methods of two-carrier channel sharing involve thesharing of a common uplink and downlink channel. The example of FIG. 13is uniquely distinct from the traditional channel sharing in that theuplink channel bandwidths to the satellite are not shared or overlappingin frequency, beam, and polarization. A digital signal processor isrequired to alter and then combine the signals to enable bandwidthefficiency on the downlink spectrum and carrier extraction on theground.

For purposes of illustration in FIG. 13, there are separate uplinktransmissions of a first source signal (signal A) 1301 a from a firstground site 1300 a (Ground Site A) to a satellite 1350 and from a secondsource signal (signal B) 1301 b from a second ground site 1300 b (GroundSite B) to a satellite 1350. Further, for purposes of illustration, adownlink transmission comprises combined source signals (signal (A+B))downlinked via a common global or regional beam 1332 to the separateground sites 1300 a, 1300 b.

It will be appreciated that more than one satellite may be involved inthe transmission of the signals. For example, each source signal may beuplinked from ground sites to distinct satellites, then crosslinked toother satellites until ultimately arriving at a satellite, where thesignals are combined. As a further example, the combined source signalmay be crosslinked to other satellites prior to downlink to the ground.

Referring again to FIG. 13, two ground site terminals 1300 a, 1300 b cansend each other information via separate uplink spot beams 1331 a, 1331b and a common downlink global or regional beam 1332 using the samedownlink spectrum. In some embodiments, each signal source is arepresentation of any arbitrary source of electronically-transmittedinformation via a communication medium. The source signals (A, B) mayarrive or originate at Ground Site A 1301 a and Ground Site B 1301 b.The sources for the signals in the example of FIG. 13 may be located atthe ground sites, but it will be appreciated that the signal sources mayoriginate and be modulated anywhere outside of the ground sites 1300 a,1300 b and then transmitted to the ground sites.

In some embodiments, prior to uplink transmission, the signal source isprovided to a modulator 1302 a, 1302 b at the respective ground sites1300 a, 1300 b for implementing modulation and coding schemes. At theground sites, one or both of Signal A 1301 a and Signal B 1301 b may bemodulated by modulators 1302 a, 1302 b using one or more furthermodulation methods (e.g., amplitude shift, phase shift, group delay,spectral inversion, and/or pseudo-noise coding). Both Signal A 1301 aand Signal B 1301 b exit their respective modems similar communicationequipment and traverse an uplink transmission path 1303 a, 1303 btypically consisting of coaxial cables, waveguides, filters, andamplifiers leading to a transmitting antenna 1307 a, 1307 b for uplinktransmission to the satellite. In the example of FIG. 13, Signal A 1301a is uplinked to satellite 1350 by antenna 1307 a over a first pathwayand Signal B 1301 b is uplinked to satellite 1350 by antenna 1307 b overa second pathway. In this example, Signal A 1301 a and Signal B 1301 bare transmitted to the satellite 1350 via orthogonal pathwayscomprising, for example, separate frequencies, beams, or polarizations.

In some embodiments, the source modulation method applied to sourcesignals by modulators 1302 a, 1302 b comprises a Digital VideoBroadcasting (DVB) standard. For example, the method of sourcemodulation may be DVB-S2 or DVB-S2X.

In some embodiments, the method of modulation applied to source signalsby modulators 1302 a, 1302 b comprises at least one Amplitude PhaseShift Key (APSK), Frequency Division Multiple Access (FDMA), TimeDivision Multiple Access (TDMA), Code Division Multiple Access (CDMA),and/or a multiplexing method. In some embodiments, one or more similarmodulation methods may be used for purposes of applying the furthermodulation to the source signals. In the embodiment of FIG. 13, thesatellite uplink paths 1351 a, 1351 b are not limited to, but typicallycomposed of, one or more receive (Rx) antennas, a low-noise amplifier, afilter, a digital down converter, and miscellaneous switches, cables,and waveguides. Received source signals may or may not share some commonsatellite components as they are routed from their respective Rxantennas to their respective DSP ports on-board satellite 1352 a, 1352b. One or more DSPs 1353 may alter and combine the signals to enablegreater bandwidth efficiency on downlink 1332. The DSP 1353 may digitizeanalog signals using an Analog-to-Digital Converter (ADC). Thesedigitalized signals may be filtered and may be routed to either anapplication specific integrated circuit (ASIC) or field programmablegate array (FPGA) in which the DSP 1353 may apply transforms andmanipulations to further modulate the signals (e.g., by amplitude shift,phase shift, group delay, and/or spectral inversion). Additionally oralternately, the DSP 1353 apply Pseudorandom Noise (PN) coding. Aspreviously discussed, the DSP 1353 of satellite 1353 combines Signal Aand Signal B such that they overlap in frequency. Embodiments maycomprise either or both regenerative and non-regenerative digital signalprocessor implementations.

In some embodiments, the transform applied to combine Signals A andSignal B into a combined Signal (A+B) allows the component signals to belater separated by, for example, applying an inverse transform, signalcancellation, or a signal identification method on the ground equipment1300 a and 1300 b that ultimately receives the combine the combinedSignal (A+B).

In the embodiment of FIG. 13, the combined Signal (A+B) is transmittedout of the DSP port 1354 to the satellite Tx path 1355 for transmissionto both ground sites 1300 a, 1300 b via a downlink global or regionalbeam 1332. The satellite downlink path 1355 is not limited to, but maybe comprised of, a transmit antenna, a traveling wave tube amplifier,filters, an up-converter, and miscellaneous switches, cables, andwaveguides.

In the embodiment of FIG. 13, both Ground Site A 1300 a and Ground SiteB 1300 b receive the combined signal at a corresponding receiver antenna1307 a, 1307 b. For purposes of illustration, the downlink receiverantennas at each ground site are the same as the uplink transmissionantennas 1307 a, 1307 b, but it will be appreciated that a separatereceiver and a separate transmission antenna may be used at each groundsite, which may be co-located at their respective ground sites or may bedistributed or remotely located. In some aspects of these embodiments,the received combined Signal (A+B) at each site are routed via grounddownlink pathways, 1304 a, 1304 b, to demodulators 1305 a, 1305 b ateach site that apply the inverse of the transform previously applied onthe satellite to extract the desired signal. Ground Site A extracts andreceives Signal B 1306 a and Ground Site B extracts and receives SignalA 1306 b from the combined signal. In some embodiments, the respectivedemodulators 1305 a, 1305 b apply inverse transforms, signalcancellation, or a signal identification method to extract out thedesired signal from the combined signal.

The foregoing description and embodiments have been presented forpurposes of illustration. It is not exhaustive and, as will beappreciated, the claimed invention is not limited to precise forms orembodiments disclosed herein. Modifications and adaptations of theembodiments will be apparent from consideration of the specification andpractice of the disclosed embodiments. For example, the describedimplementations have been described with reference to specificcomponents in a satellite communication system. As will be appreciated,the components can be arranged in various ways and implemented with anysuitable combination of hardware, firmware, and/or software, asapplicable. Furthermore, the disclosed systems and methods may bemodified and the components or steps may be rearranged, substituted, orotherwise changed without departing from the scope of the disclosure andthe below claims.

Computer programs, program modules, and code based on the writtendescription of the present disclosure, such as those used by the digitalsignal processors of the disclosed embodiments, are readily within thepurview of a software or system developer. The computer programs,program modules, or code can be created using a variety of programmingtechniques. For example, they can be designed in or by means of Java, C,C++, assembly language, or any such programming languages. One or moreof such programs, modules, or code can be integrated into a devicesystem or existing communications software. The programs, modules, orcode can also be implemented or replicated as firmware or circuit logic.

Moreover, while illustrative embodiments have been described herein, thescope includes any and all embodiments having equivalent elements,modifications, omissions, combinations (e.g., of aspects across variousembodiments), adaptations and/or alterations based on the presentdisclosure. The elements in the claims are to be interpreted broadlybased on the language employed in the claims and not limited to examplesdescribed in the present specification or during the prosecution of theapplication, which examples are to be construed as nonexclusive.Further, the steps of the disclosed methods can be modified in anymanner, including reordering steps and/or inserting or deleting steps.

The features and advantages of the disclosure are apparent from thedetailed specification, and thus, it is intended that the appendedclaims cover all systems and methods falling within the true spirit andscope of the disclosure. As used herein, the indefinite articles “a” and“an” mean “one or more.” Similarly, the use of a plural term does notnecessarily denote a plurality unless it is unambiguous in the givencontext. Words such as “and” or “or” mean “and/or” unless specificallydirected otherwise. Further, since numerous modifications and variationswill readily occur from studying the present disclosure, it is notdesired to limit the disclosure to the exact construction and operationillustrated and described, and accordingly, all suitable modificationsand equivalents may be resorted to, falling within the scope of thedisclosure.

Other embodiments will be apparent from consideration of thespecification and practice of the embodiments disclosed herein. It isintended that the specification and examples be considered as exampleonly, with a true scope and spirit of the disclosed embodiments beingindicated by the following claims.

1-24. (canceled)
 25. A method for use in a satellite communication system, comprising: receiving, at a satellite, from a first ground site terminal, a first satellite uplink beam based on a first source signal; receiving, at the satellite, from a second ground site terminal, a second satellite uplink beam based on a second source signal; generating, at the satellite, a combined signal comprising a first signal based on the first source signal and a second signal based on the second source signal, the first signal and the second signal having overlapping frequency; and transmitting the combined signal as part of a satellite downlink beam.
 26. The method of claim 25, wherein the method further comprises applying, at the satellite, modulation to at least one of the first source signal and the second source signal before generating the combined signal.
 27. The method of claim 26, wherein the modulation applied to at least one of the first source signal and the second source signal is used to generate at least one of the first signal and the second signal.
 28. The method of claim 27, wherein the modulation applied to at least one of the first source signal and the second source signal comprises at least one of an amplitude shift, a phase shift, a group delay, or a spectral inversion.
 29. The method of claim 25, where the first satellite uplink beam and the second satellite uplink beam are not overlapping in frequency.
 30. The method of claim 25, wherein at least one of the first source signal and the second source signal is modulated prior to transmission to the satellite based on a source modulation, the source modulation comprising at least one of Amplitude Phase Shift Key (APSK), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), or a multiplexing method.
 31. The method of claim 25, wherein the method further comprises transmitting the satellite downlink beam as a regional beam or a global beam.
 32. The method of claim 25, wherein the method further comprises cross-linking the satellite with one or more other satellites.
 33. The method of claim 25, wherein the combined signal is cross-linked to at least one other satellite before it is transmitted as part of the satellite downlink beam.
 34. The method of claim 25, wherein the combined signal transmitted as part of the satellite downlink beam is demodulated by the first ground site terminal to obtain the second source signal.
 35. The method of claim 34, wherein the combined signal is demodulated by applying at least one of an inverse transform method, a signal cancellation method, or a signal identification method.
 36. A system for satellite communications, the system comprising one or more digital signal processors at one or more satellites, the one or more digital signal processors being configured to perform operations comprising: receiving, from a first ground site terminal, a first satellite uplink beam based on a first source signal; receiving, from a second ground site terminal, a second satellite uplink beam based on a second source signal; generating, a combined signal comprising a first signal based on the first source signal and a second signal based on the second source signal, the first signal and the second signal having overlapping frequency; and transmitting the combined signal as part of a satellite downlink beam.
 37. The system of claim 36, wherein the operations further comprise applying modulation to at least one of the first source signal and the second source signal before generating the combined signal.
 38. The system of claim 37, wherein the modulation applied to at least one of the first source signal and the second source signal is used to generate at least one of the first signal and the second signal.
 39. The system of claim 38, wherein the modulation applied to at least one of the first source signal and the second source signal comprises at least one of an amplitude shift, a phase shift, a group delay, or a spectral inversion.
 40. The system of claim 36, where the first satellite uplink beam and the second satellite uplink beam are not overlapping in frequency.
 41. The system of claim 36, wherein at least one of the first source signal and the second source signal is modulated based on a source modulation, the source modulation comprising at least one of Amplitude Phase Shift Key (APSK), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), or a multiplexing method.
 42. The system of claim 36, wherein the operations further comprise transmitting the satellite downlink beam as a regional beam or a global beam.
 43. The system of claim 36, wherein the operations further comprise cross-linking the one or more other satellites.
 44. The system of claim 36, wherein the combined signal is cross-linked from a first satellite to at least one other satellite before it is transmitted as part of the satellite downlink beam.
 45. The system of claim 36, wherein the combined signal transmitted as part of the satellite downlink beam is demodulated by the first ground site terminal to obtain the second source signal.
 46. The system of claim 45, wherein the combined signal is demodulated by applying at least one of an inverse transform method, a signal cancellation method, or a signal identification method.
 47. A non-transitory computer-readable medium storing instructions executable by one or more hardware processors of one or more satellites to carry out operations comprising: receiving, from a first ground site terminal, a first satellite uplink beam based on a first source signal; receiving, from a second ground site terminal, a second satellite uplink beam based on a second source signal; generating, a combined signal comprising a first signal based on the first source signal and a second signal based on the second source signal, the first signal and the second signal having overlapping frequency; and transmitting the combined signal as part of a satellite downlink beam.
 48. The non-transitory computer-readable medium of claim 47, wherein the operations further comprise applying modulation to at least one of the first source signal and the second source signal before generating the combined signal.
 49. The non-transitory computer-readable medium of claim 48, wherein the modulation applied to at least one of the first source signal and the second source signal is used to generate at least one of the first signal and the second signal.
 50. The non-transitory computer-readable medium of claim 49, wherein the modulation applied to at least one of the first source signal and the second source signal comprises at least one of an amplitude shift, a phase shift, a group delay, or a spectral inversion.
 51. The non-transitory computer-readable medium of claim 47, where the first satellite uplink beam and the second satellite uplink beam are not overlapping in frequency.
 52. The non-transitory computer-readable medium of claim 47, wherein the operations further comprise cross-linking the one or more other satellites.
 53. The non-transitory computer-readable medium of claim 47, wherein the combined signal is cross-linked from a first satellite to at least one other satellite before it is transmitted as part of the satellite downlink beam.
 54. The non-transitory computer-readable medium of claim 47, wherein the combined signal transmitted as part of the satellite downlink beam is demodulated by the first ground site terminal to obtain the second source signal.
 55. The non-transitory computer-readable medium of claim 54, wherein the combined signal is demodulated by applying at least one of an inverse transform method, a signal cancellation method, or a signal identification method. 